♫ This is the dawning of the age of articular cartilage ♫

October 6, 2010

Isn’t it funny how often an idea seems to pop up all over the place at about the same time?  The classic example is the independent and more or less simultaneous invention of calculus by both Isaac Newton and Wilhelm Leibniz, but similar kinds of things seem to happen quite often.

And there’s something similar going on right now.  After a century of everyone ignoring the role of cartilage in dinosaur anatomy, suddenly everyone’s up and running all at once:

  • Here at SV-POW!, Matt, Darren and I have been running the series on camel necks (which by the way isn’t over yet — stay tuned!)  In that series we have repeatedly made the point that “it is useless to try to reach conclusions about neck posture based on osteology alone. We need to understand the soft-tissue systems — especially the articular cartilage — as well”.
  • Meanwhile, over on his blog Jurassic Journeys, Matt Bonnan has been writing about “long bones and the space between“, emphasising how we can’t really understand sauropod locomotion when we don’t know the true sizes and shapes that the long-bones had in life.
  • Independently of that, Heinrich Mallison, on the Palaeontologia Electronica blog, wrote about the importance of cartilage in his Plateosaurus digital modelling projects.  I highly recommend reading this very relevant article if only for its section headings, which sum up the state of play perfectly: Ask your doctor for advice // Palaeontology is an interdisciplinary science — we just tend to forget // Have you ever read the Journal of International Orthopaedics? // How do these go together? Where’s the manual? HELP!
  • The next thing we know, Casey Holliday and his colleagues wrote about the same issue — not merely blogging, but producing a long-awaited peer-reviewed article in PLoS ONE, “Cartilaginous Epiphyses in Extant Archosaurs and Their Implications for Reconstructing Limb Function in Dinosaurs“.  Casey and his group have gone much further than the rest of us: rather than just whining about the problem of cartilage, they’ve taken steps to solve it — see below for details.
  • Finally, it turns out that Dave Hone has had a blog entry on this subject in the works at Archosaur Musings for a year or more.

It’s a pretty amazing confluence of thought, and the Holliday et al. paper really couldn’t have come at a better time.  It gives us, for the first time, qualitative estimates of the thickness of articular cartilage in limb-bones.  They dissected birds and alligators, measured their limb bones before and after the removal of their cartilage caps, compared the measurements, and determined what they called cartilage correction factors (CCFs) that quantify the increase in limb length when cartilage is included.  They also examined the osteological correlates of extensive articular cartilage, and drew conclusions about the likely form and function of these structures in sauropods (and, yes, I suppose, other dinosaurs as well).

This all ties in nicely with a long-running background project of mine, first presented at Progressive Palaeontology in 2005, and then again at the German sauropod-fest in 2008.  While Holliday et al. were investigating the thickness of articular cartilage, I was thinking in a very naive way about its area as part of a study tentatively entitled Upper limits on the mass of land animals estimated through the articular area of limb-bone cartilage.  The slides for the talk are available, and contain a Godzilla joke that will be hauntingly familiar to anyone who saw my talk on neck elongation at SVPCA this year.

Poorly executed slide from my 2005 Progressive Palaeontology talk. Despite the clumsy graphics, the point should be clear: that the area of articular cartilage available to withstand static and locomotory forces depends hugely on how extensive the cartilage caps are, and on their shape.

I ought to be clear that my work on this was very preliminary and that I am, as usual, years behind where I wanted to be in terms of getting this written up rigorously.  In fact the talk ended with a slide in which I pointed that I was pretty confident that “my figures are correct within a factor of 756”.  And I stand by that :-)

My point is just this: suddenly there’s a visible swell of palaeontologists all saying the same thing: that we can’t expect to understand how the skeletons of extinct animals worked by looking only at their bones, which is a bit of a shame when their bones are usually all we have.  The Holliday et al. paper (2010) is a very welcome first step towards wrasslin’ with this problem as it deserves.

Oh, and it’s open access — go read it!


15 Responses to “♫ This is the dawning of the age of articular cartilage ♫”

  1. Heinrich Mallison Says:

    Another of these problems that a bunch of people keep fiddling with, in otherwise barely or even unrelated research. I’m glad that the Holliday et al. paper is out, combined with my favorite (Graf et al. 1993( it finally will put an end to those eternal reviewers’ comments on my papers that “cartilage must have been thin because of the limits of diffusion”.


  2. […] This post was mentioned on Twitter by Chris Rowan, JP – Research Lab. JP – Research Lab said: ♫ This is the dawning of the age of articular cartilage ♫: Isn’t it funny how often an idea seems to pop up all ov… http://bit.ly/c2eZqX […]

  3. Andrea Cau Says:

    Sorry for the OT, but, if this is a fake, it’s the best ever done:

    [Mike says: sorry, Andrea, but I’d rather not give that any publicity on here until I’ve had time to think about it a bit more. Hope you understand.]

  4. Andrea Cau Says:

    I understand, and sorry for my OT comment, Mike. Since I consider this THE sauropod blog, my first reaction was to share that link with you. ;-)

  5. LeeB Says:

    Thanks Andrea.

    That is going to be quite a controversial paper.


  6. Edoard Says:

    This is amazing

  7. Zach Miller Says:

    You’re gonna have to post the Godzilla slide now.

  8. […] ♫ This is the dawning of the age of articular cartilage ♫ […]

  9. I have nothing to say but “Great!” :-D
    (goes off to read papers)

  10. […] it got washed away in the flood of camel necks (which by the way is not over yet), and then in the festival of articular cartilage, then by the whole “Amphicoelias brontodiplodocus” thing and the subsequent discussion […]

  11. William Miller Says:

    >>You’re gonna have to post the Godzilla slide now.

    The Godzilla slide is up at Tetrapod Zoology here: http://scienceblogs.com/tetrapodzoology/2010/11/science_of_godzilla_2010.php

  12. […] When I last posted on this topic, it was before the Society of Vertebrate Paleontology meeting in Pittsburgh, and I was gearing up to share some of my lab’s recent research on reconstructing limb joint cartilage in living dinosaur relatives: birds and crocodylians.  Moreover, Mike Taylor has done a nice job on his blog talking about this particular issue as well. […]

  13. […] interest in articular cartilage is booming right now, as Mike blogged about here. In addition to the Dread Olecranon of Kentrosaurus, see the Dread Elbow Condyle-Thingy […]

  14. […] extensive articular cartilage (typical of many aquatic animals, especially some amphibians) and would make a sauropod jealous. The relatively homogenous vertebral column, without much differentiation from head to tail, is […]

  15. […] we account for any shrinkage in the molding and casting process, and the gaps between the bones for joint cartilage should probably be much wider, so the actual shoulder height of this individual might have been […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: